The present invention relates to a subsoil structure for sodded ground, and more particularly to a subsoil structure for a putting green in a golf course, which subsoil structure has good water- and fertilizer-retentivity while being excellent in water-permeability. By such structure the number of watering times can be extremely reduced, while even in the case of rain fertilizers and the like can be prevented from flowing out.
Conventionally, drainage for a putting green in a golf course has been conducted with the use of a drain pipe 10 buried under the green, as shown in FIG. 2. As the drain pipe 10 is used a synthetic resin pipe, unglazed ceramic pipe or the like which is provided with a multiplicity of apertures in the circumferential wall thereof. The diameter of the drainage pipe 10 depends upon whether or not the district where the golf course is situated is rich in rainfall, the area of the putting green or the like. However, in general a branch pipe 10a has a diameter of about 5 to 10 cm, while a trunk pipe 10b has a diameter of about 10 to 15 cm. Rainwater penetrating into the green is introduced into the branch pipe 10a through the apertures in the circumferential wall thereof, collected to the trunk pipe 10b, and concentratedly drained at one or two spots.
However, most of the putting greens now available are of sabulous green in which much sand is used to prevent root rot of grass. For this reason, with the concentrated drainage system using the buried drainage pipe, even a small amount of rain rapidly penetrates the sand layer and easily flows out. Agricultural chemicals or fertilizers that are used to maintain or control the grass also flow out together with the rainwater. This results in one of the causes accounting for environmental pollution in areas downstream of the golf course.
In summer especially, watering the putting green is required for growing and maintaining the grass. With the conventional concentrated drainage system, however, a sabulous sand green of bent grass would require watering at least about twice per day in summer, even if a water-retaining material such as perlite or pumice is incorporated as an improving material in the sabulous green. Such watering requires time and labor.
In view of the above-mentioned circumstances, an object of the present invention is to provide a subsoil structure for sodded ground, which is capable of preventing an easy outflow of agricultural chemicals or fertilizers and extremely reducing the number of watering times.